In a typical wireless communications network (for example, Long Term Evolution (LTE)), selection of uplink shared data channels is based on a scheduling/grant mechanism and completely controlled by a base station (BS). A complete data transmission process usually includes four steps: a scheduling request, a scheduling grant, data transmission, and transmission feedback. In this mechanism, user equipment (UE) first sends an uplink scheduling request to the BS; after receiving the request, the BS sends an uplink grant to the UE to notify the UE of an uplink transmission resource allocated to the UE; and then the UE performs data transmission on the granted uplink transmission resource accordingly.
Large-scale user access is one of typical application scenarios of a next-generation communications network. During massive user access, if the foregoing scheduling/grant mechanism is still used, huge signaling transmission overheads and BS resource allocation scheduling pressure are caused, and a significant transmission delay is also caused. In view of this, the next-generation communications network uses a grant-free transmission mode to support massive user access.
In a grant-free transmission mode, a base station does not schedule a transmission resource for user equipment. When a plurality of user equipments needs to simultaneously transmit data, the user equipments usually perform data transmission on a preconfigured common time-frequency resource in a contention-based manner. A grant-free transmission process may be simplified into two steps: data transmission and transmission feedback, thereby reducing signaling overheads and a transmission delay. In the grant-free transmission mode, the base station knows neither identification information of the user equipment nor information about a time-frequency resource occupied by the user equipment during data transmission. Therefore, the base station cannot perform feedback on the data transmission of the user equipment by using the feedback manner in the prior art. However, if a user identity is directly fed back to user equipment whose data is successfully decoded, to indicate that transmission succeeds, resource utilization efficiency may be reduced due to excessive bits occupied by the user identity.
Therefore, how to efficiently use radio transmission resources to perform feedback on grant-free transmission of user equipment is a problem that urgently needs to be resolved.